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I have the following code:

\documentclass{article}
\begin{document}
$
M = \bordermatrix{~ & x & y \cr
              A & 1 & 0 \cr
              B & 0 & 1 \cr}
$
\end{document}

But this code makes a matrix with () and i would like it to be with [] How do i do this?

share|improve this question
    
There is also a kbordermatrix (look at the last item for documentation) environment available for such purposes. –  percusse May 9 '12 at 12:20
    
See Where is the \matrix command? –  Werner May 9 '12 at 15:52

2 Answers 2

up vote 16 down vote accepted

An almost direct modification of \bordermatrix:

\documentclass{article}
\makeatletter
\def\bbordermatrix#1{\begingroup \m@th
  \@tempdima 4.75\p@
  \setbox\z@\vbox{%
    \def\cr{\crcr\noalign{\kern2\p@\global\let\cr\endline}}%
    \ialign{$##$\hfil\kern2\p@\kern\@tempdima&\thinspace\hfil$##$\hfil
      &&\quad\hfil$##$\hfil\crcr
      \omit\strut\hfil\crcr\noalign{\kern-\baselineskip}%
      #1\crcr\omit\strut\cr}}%
  \setbox\tw@\vbox{\unvcopy\z@\global\setbox\@ne\lastbox}%
  \setbox\tw@\hbox{\unhbox\@ne\unskip\global\setbox\@ne\lastbox}%
  \setbox\tw@\hbox{$\kern\wd\@ne\kern-\@tempdima\left[\kern-\wd\@ne
    \global\setbox\@ne\vbox{\box\@ne\kern2\p@}%
    \vcenter{\kern-\ht\@ne\unvbox\z@\kern-\baselineskip}\,\right]$}%
  \null\;\vbox{\kern\ht\@ne\box\tw@}\endgroup}
\makeatother

\begin{document}
$
M = \bbordermatrix{~ & x & y \cr
              A & 1 & 0 \cr
              B & 0 & 1 \cr}
$
\end{document}

I acted on \left( and \right), but also changed the value given to \@tempdima, smaller because brackets are slimmer than parentheses.

If you don't want such a messy code, just do

\usepackage{etoolbox}
\let\bbordermatrix\bordermatrix
\patchcmd{\bbordermatrix}{8.75}{4.75}{}{}
\patchcmd{\bbordermatrix}{\left(}{\left[}{}{}
\patchcmd{\bbordermatrix}{\right)}{\right]}{}{}

that does exactly the same changes.

enter image description here

share|improve this answer
    
Thank you:D Been looking for a few hours now;) –  Andreas May 9 '12 at 12:11

Following Herbert Voss' excellent mathmode document, you can redefine the bordermatrix command to take an optional argument that determines the delimeters

enter image description here

Note that Herbert also details that the amsmath package offers the same or better macros/environments

\documentclass{article}
\makeatletter
\newif\if@borderstar
\def\bordermatrix{\@ifnextchar*{%
\@borderstartrue\@bordermatrix@i}{\@borderstarfalse\@bordermatrix@i*}%
}
\def\@bordermatrix@i*{\@ifnextchar[{\@bordermatrix@ii}{\@bordermatrix@ii[()]}}
\def\@bordermatrix@ii[#1]#2{%
\begingroup
\m@th\@tempdima8.75\p@\setbox\z@\vbox{%
\def\cr{\crcr\noalign{\kern 2\p@\global\let\cr\endline }}%
\ialign {$##$\hfil\kern 2\p@\kern\@tempdima & \thinspace %
\hfil $##$\hfil && \quad\hfil $##$\hfil\crcr\omit\strut %
\hfil\crcr\noalign{\kern -\baselineskip}#2\crcr\omit %
\strut\cr}}%
\setbox\tw@\vbox{\unvcopy\z@\global\setbox\@ne\lastbox}%
\setbox\tw@\hbox{\unhbox\@ne\unskip\global\setbox\@ne\lastbox}%
\setbox\tw@\hbox{%
$\kern\wd\@ne\kern -\@tempdima\left\@firstoftwo#1%
\if@borderstar\kern2pt\else\kern -\wd\@ne\fi%
\global\setbox\@ne\vbox{\box\@ne\if@borderstar\else\kern 2\p@\fi}%
\vcenter{\if@borderstar\else\kern -\ht\@ne\fi%
\unvbox\z@\kern-\if@borderstar2\fi\baselineskip}%
\if@borderstar\kern-2\@tempdima\kern2\p@\else\,\fi\right\@secondoftwo#1 $%
}\null \;\vbox{\kern\ht\@ne\box\tw@}%
\endgroup
}
\makeatother


\begin{document}
$
M = \bordermatrix[{[]}]{%
            & x & y \cr
          A & 1 & 0 \cr
          B & 0 & 1 }
$

$
M = \bordermatrix[\{\}]{%
            & x & y \cr
          A & 1 & 0 \cr
          B & 0 & 1 }
$
\end{document}
share|improve this answer
    
The link is broken. Is this it? tex.ac.uk/ctan/info/math/voss/mathmode/Mathmode.pdf –  Joel Sjögren Jul 22 at 19:33
    
@JoelSjögren indeed - thanks, I have updated it :) or else texdoc mathmode will also work –  cmhughes Jul 22 at 19:37

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